This invention relates to cleaning of air ports and smelt spouts in recovery boilers.
In operation of recovery boilers, it is necessary to clean the air ports of build up material that collects and, over time, obstructs the air ports. One style of known port cleaner employs a “cookie cutter” type operation, wherein a fixed size and shape punch is periodically moved into the air port in an attempt to break away any built up material. This type device travels through a single fixed actuation path.
However, over time, bushings will wear, which alters the exact operation path through which the punch will move. This can result in the punch getting caught on the port, for example,
An example of a prior art device is illustrated schematically in FIG. 1 and FIG. 2. In FIG. 1, which is a top sectional view of an installation of the prior art device, a wind box 10 is provided on the outside wall of the recover boiler tubes 12. Several air ports 14 enable entry of combustion air 16 (which is supplied to the wind box by means not shown) into the boiler interior. The prior art device employs a ring-shaped gap area 18 around the air ports, which are able receive hollow sleeves 20 therein. The sleeves are mounted to a compression air cylinder 22, which is actuable to cause the sleeves to translate into and out of the air ports on an insertion stroke. The sleeves are in the retracted state in FIG. 1 and are in the inserted state in FIG. 2. The hollow sleeve allows entry of air therethrough into the air port.
The tip portion of the sleeve comprises a horn that enters into the airport is shaped similar to the shape of the airport opening, but is slightly smaller. The outside perimeter of the horn acts to clean the air port by entry into the air port, and thereby scraping or knocking off built up material. An attempt to provide damping (i.e. some air flow control) is made by throttling the horn within the volute of the air port. However, the hollow nature of the sleeve and horn opening allows little actual flow control, as airflow will go around the opening between the sleeve and airport and through the hollow tube portion.